Bégin-Heick N
Department of Biochemistry, University of Ottawa, Ontario, Canada.
Biochem J. 1990 May 15;268(1):83-9. doi: 10.1042/bj2680083.
The abundance of the alpha and beta subunits of the GTP-binding proteins (G-proteins) that transduce hormonal messages to adenylate cyclase was assessed in adipocyte membranes from lean (+/+) and obese (ob/ob) mice, using ADP-ribosylation with bacterial toxin and immunodetection. Both methods revealed two Gs alpha species (48 and 42 kDa) in the membranes. Compared with those of lean mice, the membranes from obese mice contained substantially less of the 48 kDa species of Gs alpha, as assessed by both methods. ADP-ribosylation by pertussis toxin showed that only half as much ADP-ribose was incorporated into Gi alpha in the membranes from obese as compared with lean mice. Immunodetection revealed two separate Gi alpha peptides (39 and 40 kDa) and showed that the 40 kDa species was less abundant in the membranes from obese mice, whereas the amount of the 39 kDa species was similar in membranes from both lean and obese animals. Based on ADP-ribosylation assays, in membranes from lean mice the ratio Gs alpha/Gi alpha was 1:16, whereas in the membranes from obese mice it was 1:10. Similar amounts of immunodetectable beta peptide were found in both types of membranes. On the basis of the currently accepted dissociation model of adenylate cyclase activation, the decrease in the abundance of the Gi alpha subunit in adipocyte membranes from obese mice could account for the abnormal kinetics of the enzyme in these membranes.
利用细菌毒素进行ADP核糖基化和免疫检测，评估了将激素信息传递给腺苷酸环化酶的GTP结合蛋白（G蛋白）的α和β亚基在瘦型（+/+）和肥胖型（ob/ob）小鼠脂肪细胞膜中的丰度。两种方法均在膜中检测到两种Gsα亚型（48 kDa和42 kDa）。与瘦型小鼠相比，两种方法评估结果均显示，肥胖型小鼠的膜中48 kDa的Gsα亚型含量显著减少。百日咳毒素进行的ADP核糖基化显示，与瘦型小鼠相比，肥胖型小鼠膜中掺入Giα的ADP核糖量仅为其一半。免疫检测揭示了两种不同的Giα肽（39 kDa和40 kDa），并表明40 kDa的亚型在肥胖型小鼠的膜中含量较少，而39 kDa亚型在瘦型和肥胖型动物的膜中的含量相似。基于ADP核糖基化分析，瘦型小鼠膜中Gsα/Giα的比例为1:16，而肥胖型小鼠膜中的比例为1:10。两种类型的膜中免疫可检测的β肽含量相似。根据目前公认的腺苷酸环化酶激活解离模型，肥胖型小鼠脂肪细胞膜中Giα亚基丰度的降低可解释这些膜中该酶的异常动力学。
